Because of excessive dependence on its screen as input and output devices, in addition to a variety of system software features and services, a smartphone's battery power consumption is very fast. To solve this problem, there are many prior art technologies for optimizing or saving the battery power consumption of a smartphone. Nonetheless, these power-saving functions usually do not provide a user of the smartphone enough information as to the effect of these power-saving functions, or how long the usage time of the smartphone has been extended. As a result, the user is unable to make reasonable arrangements to the usage of the smartphone.